The present invention relates to a device for setting and automatic adjustment of the tractive force of the cable of an overhead winch for a ski slope preparation and maintenance machine.
To maintain a predetermined pulling force of a cable there are known winch adjustment devices for influencing a controllable winch operation in such a manner that exceeding or falling short of the adjusted tractive forces is avoided. Increased stress on the cable can lead to cable breakage with serious consequences. In addition the adjustment devices of known type do not allow for the dynamics of a vehicle on which they are installed and in particular the different angular positions which the cable can assume with respect to the vehicle. Due to the fact that the cable force adjustment devices in known winches are only adjustable for the nominal admissible cable tension, allowance is not made for vehicle travel circumstances and the cable is subject to tractive forces of needless magnitude for performance of certain ooperations. This needlessly reduces cable life.
The general purpose of the present invention is to remedy the above mentioned shortcomings by making available a device for setting and automatic adjustment of the tractive force allowing for the circumstances of a ski slope preparation and maintenance machine with the purpose of making the necessary tractive force available at all times but at the same time limiting it to the amount strictly necessary. In addition a nominal tractive force should be set automatically.
This purpose is achieved in accordance with the present invention by a device for setting and automatic adjustment of the tractive force of an overhead winch for a ski slope preparation and maintenance machine.
With the aid of an adjustment control unit and an algorithm deposited on it and from different measurements taken by sensors a nominal tractive force is determined. The nominal value is made up of the hydrostatic cable operation pressure of travel and the cable angle in relation to the vehicle as well as a correction factor predetermined by the operator. In a closed adjustment circuit located downstream the nominal value thus taken is compared with the real value measured by a dynamometric pin and the tractive force is adjusted to the nominal value.
As a measurement of the necessary tractive force there is the travel operation pressure. If for example the winch cable is located forward in the direction of travel and a high pressure is located on the xe2x80x98leading sidexe2x80x99 of the travel operation, then the winch tractive force should also be chosen correspondingly high. But if the pressure is applied on the xe2x80x98trailing sidexe2x80x99 to the winch cable directed in the direction of travel it means that the overhead winch is working against the travel traction. In this case the winch tractive force should be set very low.
In addition the winch tractive force should be reduced if it is engaged transversely to the direction of travel. If because of unfavorable snow conditions (for example fresh snow) the adjustment control unit supplied erroneous nominal values for tractive force the operator has the option of oversteering and specifically of making possible a tractive force increase or reduction.
Additional characteristics and advantages of the device in accordance with the present invention are set forth in the claims and the description given below of a preferred embodiment with reference to the annexed drawings.